In 2016, the order Mononegavirales was emended through the addition of two new families (Mymonaviridae and Sunviridae), the elevation of the paramyxoviral subfamily Pneumovirinae to family status (Pneumoviridae), the addition of five free-floating genera (Anphevirus, Arlivirus, Chengtivirus, Crustavirus, and Wastrivirus), and several other changes at the genus and species levels. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV).

Spring viremia of carp (SVC) is an important disease affecting cyprinids, mainly common carp Cyprinus carpio. The disease is widespread in European carp culture, where it causes significant morbidity and mortality. Designated a notifiable disease by the Office International des Epizooties, SVC is caused by a rhabdovirus, spring viremia of carp virus (SVCV). Affected fish show destruction of tissues in the kidney, spleen and liver, leading to hemorrhage, loss of water-salt balance and impairment of immune response. High mortality occurs at water temperatures of 10 to 17 degrees C, typically in spring. At higher temperatures, infected carp develop humoral antibodies that can neutralize the spread of virus and such carp are protected against re-infection by solid immunity. The virus is shed mostly with the feces and urine of clinically infected fish and by carriers. Waterborne transmission is believed to be the primary route of infection, but bloodsucking parasites like leeches and the carp louse may serve as mechanical vectors of SVCV. The genome of SVCV is composed of a single molecule of linear, negative-sense, single-stranded RNA containing 5 genes in the order 3'-NPMGL-5' coding for the viral nucleoprotein, phosphoprotein, matrix protein, glycoprotein, and polymerase, respectively. Polyacrylamide gel electrophoresis of the viral proteins, and sequence homologies between the genes and gene junctions of SVCV and vesicular stomatitis viruses, have led to the placement of the virus as a tentative member of the genus Vesiculovirus in the family Rhabdoviridae. These methods also revealed that SVCV is not related to fish rhabdoviruses of the genus Novirhabdovirus. In vitro replication of SVCV takes place in the cytoplasm of cultured cells of fish, bird and mammalian origin at temperatures of 4 to 31 degrees C, with an optimum of about 20 degrees C. Spring viremia of carp can be diagnosed by clinical signs, isolation of virus in cell culture and molecular methods. Antibodies directed against SVCV react with the homologous virus in serum neutralization, immunofluorescence, immunoperoxidase, or enzyme-linked immunosorbent assays, but they cross-react to various degrees with the pike fry rhabdovirus (PFR), suggesting the 2 viruses are closely related. However, SVCV and PFR can be distinguished by certain serological tests and molecular methods such as the ribonuclease protection assay.

Infectious hematopoietic necrosis virus (IHNV) is a rhabdoviral pathogen that infects wild and cultured salmonid fish throughout the Pacific Northwest of North America. IHNV causes severe epidemics in young fish and can cause disease or occur asymptomatically in adults. In a broad survey of 323 IHNV field isolates, sequence analysis of a 303 nucleotide variable region within the glycoprotein gene revealed a maximum nucleotide diversity of 8?6 %, indicating low genetic diversity overall for this virus. Phylogenetic analysis revealed three major virus genogroups, designated U, M and L, which varied in topography and geographical range. Intragenogroup genetic diversity measures indicated that the M genogroup had three-to fourfold more diversity than the other genogroups and suggested relatively rapid evolution of the M genogroup and stasis within the U genogroup. We speculate that factors influencing IHNV evolution may have included ocean migration ranges of their salmonid host populations and anthropogenic effects associated with fish culture. INTRODUCTIONInfectious hematopoietic necrosis virus (IHNV) is a rhabdovirus that causes acute, systemic disease in salmonid fish and also occurs in asymptomatic fish hosts. The virus is currently endemic throughout the Pacific Northwest of North America, with a contiguous range extending from Alaska to California and inland to Idaho. Within this geographical area the host range of IHNV includes five species of Pacific salmon, Atlantic salmon and several trout species (Wolf, 1988;Bootland & Leong, 1999). The first reported epidemics of IHNV occurred in sockeye salmon (Oncorhynchus nerka) fry at Washington and Oregon fish hatcheries during the 1950s (Rucker et al., 1953;Guenther et al., 1959;Wingfield et al., 1969). Surveys indicated that IHNV was endemic in sockeye throughout Alaska by 1974(Grischkowsky & Amend, 1976, but the virus was not widespread in Washington and Oregon through the 1970s (Amend & Wood, 1972; Mulcahy et al., 1980;Pilcher & Fryer, 1980). Subsequently, two virus emergence events occurred in which IHNV became endemic in rainbow trout (O. mykiss) throughout the Hagerman Valley trout farming industry in southern Idaho between 1977(Busch, 1983 and in salmonids of the middle and lower Columbia River basin in the early 1980s (Groberg, 1983;Groberg & Fryer, 1983). In addition to cultured fish, IHNV is endemic in many wild salmonid stocks in the Pacific Northwest (Bootland & Leong, 1999).Due to the extensive economic losses caused by IHNV in fish culture facilities, the virus has been well characterized in biological, immunological and molecular biological studies (for reviews, see Wolf, 1988;Bootland & Leong, 1999). IHNV is the type species of the genus Novirhabdovirus, within the family Rhabdoviridae. Similar to other rhabdoviruses, IHNV has a linear single-stranded, negative-sense RNA genome of approximately 11 000 nucleotides. The IHNV genome contains six genes in the order 39-N-P-M-G-NV-L-59, representing the nucleocapsid, phosphoprotein, matrix protein, glyco...

In February 2019, following the annual taxon ratification vote, the order Mononegavirales was amended by the addition of four new subfamilies and 12 new genera and the creation of 28 novel species. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV).